This invention relates to a matrix switching device and more particularly, but not by way of limitation, to a universal matrix switching device used with an automatic test system under computer control for interfacing with a unit to be tested.
Heretofore, matrix units exhibited poor transmission characteristics at high frequency. Above one metahertz serious loss would occur from radiation or from signal reflections due to impedance mismatches with 50 OHM coaxial interfaces commonly found in test systems. To have good high frequency transmission qualities the matrix must provide for impedance matching and for isolation between signal paths.
Prior matrix switching devices have had uniform spacing of conductors in their design. As as result a signal and its return have differing amounts of interferences induced in them from adjacent signal paths. The uniform layout of signal lines results in poor common mode rejection quality. This problem is intensified as the frequency of operation is increased.
Also, prior matrix switching devices have relied on a single relocatable actuator to close cross-point switches. In an automatic test application this design is unsuitable because the single actuator will have to travel excessively long distances to provide the sequential switching at random locations. Consequentially, both excessive wear and time delays will be incurred in its operation. Additionally, a single actuator design concentrates all switch operations on the one actuator causing a reduction in the unit's operating life.
Prior matrix switching devices have not had the capability to open individual switches in the matrix. A reset of all switches is necessary to reset one switch. This is a severe limitation in automatic test applications.
Various switching devices are described in the following U.S. Patents: U.S. Pat. No. 3,191,040 to Critchlow, U.S Pat. No. 3,219,927 to Topp Jr., et al, U.S. Pat. No. 3,631,374 to Cartelli, U.S. Pat. No. 3,796,848 to Southworth, Jr., U.S. Pat. No. 3,905,020 to Knox, U.S. Pat. No. 4,215,420 to Kassakian, U.S. Pat. No. 4,326,191 to Schlecht et al. None of these prior art patents specifically describe and point out the unique features and combination of structure of the subject universal matrix switching device as described herein.